Soft-γ-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are slowly rotating, isolated neutron stars that sporadically undergo episodes of long-term flux enhancement (outbursts) generally ...accompanied by the emission of short bursts of hard X-rays. This behaviour can be understood in the magnetar model, according to which these sources are mainly powered by their own magnetic energy. This is supported by the fact that the magnetic fields inferred from several observed properties of SGRs and AXPs are greater than-or at the high end of the range of-those of radio pulsars. In the peculiar case of SGR 0418+5729, a weak dipole magnetic moment is derived from its timing parameters, whereas a strong field has been proposed to reside in the stellar interior and in multipole components on the surface. Here we show that the X-ray spectrum of SGR 0418+5729 has an absorption line, the properties of which depend strongly on the star's rotational phase. This line is interpreted as a proton cyclotron feature and its energy implies a magnetic field ranging from 2 × 10(14) gauss to more than 10(15) gauss.
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Two Missions, One Microquasar Bignami, Giovanni F.
Science (American Association for the Advancement of Science),
12/2009, Volume:
326, Issue:
5959
Journal Article
Peer reviewed
It has been on the suspect list for more than 30 years, but now we know for sure, smoking gun and all, that x-ray source number 3 in the constellation of Cygnus (Cyg X-3) emits gamma rays. After many ...near (and wide-of-the-mark) misses, we now have incontrovertible evidence coming from two independent gamma-ray telescopes, AGILE (1) and Fermi (2), the latter reported on page 1512 of this issue.
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Since Galileo looked skyward 400 years ago, telescopes have evolved to provide a broader and deeper understanding of the universe.
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4.
Astronomy. Gamma rays and neutron stars Bignami, Giovanni F
Science (American Association for the Advancement of Science),
2008-Nov-21, 20081121, Volume:
322, Issue:
5905
Journal Article
Peer reviewed
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We present numerical calculations of the photon-light-pseudoscalar-boson (LPB) production in the recently discovered binary pulsar system J0737-3039. Light pseudoscalar bosons oscillate into photons ...in the presence of strong magnetic fields. In the context of this binary pulsar system, this phenomenon attenuates the light beam emitted by one of the pulsars, when the light ray goes through the magnetosphere of the companion pulsar. We show that such an effect is observable in the gamma-ray band since the binary pulsar is seen almost edge-on, depending on the values of the LPB mass and on the strength of its two-photon coupling. Our results are surprising in that they show a very sharp and significant (up to 50%) transition probability in the gamma-ray (> tens of MeV) domain. The observations can be performed by the upcoming NASA GLAST mission.
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In this Letter we study the propagation of light in the neighborhood of magnetized neutron stars. Because of the optical properties of quantum vacuum in the presence of a magnetic field, the light ...emitted by background astronomical objects is deviated, giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect, and we discuss the possibility of its observation. We show that this effect could be detected by monitoring the evolution of the recently discovered double neutron star system J0737-3039.
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